In automotive engineering more and more integrated circuits, for example in the form of microprocessors or microcontrollers, are used. For their power supply usually an external blocking capacitor connected in parallel manner between a supply input of the integrated circuit and a circuit carrier ground as well as a voltage source connected parallel thereto are provided. Both the blocking capacitor and the voltage source are directly connected with the circuit carrier ground. The voltage source charges the blocking capacitor, the energy supplied to the integrated circuit being extracted from the blocking capacitor by means of a discharging current. Hereby, a reproduction of an ideal voltage source which is as realistic as possible is to be achieved. For this purpose the blocking capacitor usually has a blocking capacity of approx. 100 nF. The described circuit arrangement is discussed in detail in WO 2006/094469 A1, to which reference is made. It is disadvantageous with the described circuit arrangement that it leads to an undesired high emission of electromagnetic energy, in particular if a clock frequency of the integrated circuit adopts higher values than 10 MHZ. The EMC-requirements of the automotive industry can then no longer be complied with.
From WO 2006/094469 A1 a circuit arrangement is known, with the aid of which an integrated circuit can be supplied with energy even with a high clock frequency, in particular in the MHz region, wherein simultaneously the emission of electromagnetic energy is significantly reduced compared with the above-described circuit arrangement and the EMC-requirements of the automotive industry can be complied with. The reduced emission is achieved by doing without the external wiring with the blocking capacitor and using instead an internal bus capacity which is anyway present within the integrated circuit. Furthermore, a supply unit with an internal resistance which is as high as possible is used in place of a low-impedance voltage source. By these measures a frequency decoupling of the charging and discharging of the internal bus capacity is achieved. Whereas the discharging of the bus capacity continues with the high clock frequency, the discharging in turn is effected with a significantly deeper frequency. Due to the fact that the high-frequency discharging process takes place in a spatially tight manner within the integrated circuit and that the charging process is low-frequent, both the charging and the discharging process do not effect a significant emission of electromagnetic energy. However, it is disadvantageous that the used internal bus capacity is only approx. 5 nF, so that voltage fluctuations arise with the supply of the circuit load, which fluctuations are caused by software-related variations of the load.